2.4. Powder X-ray diffractometry
Freeze-dried amorphous sugar samples, containing 10 wt%
NaCl, as well as pure sucrose formulation were placed on a sample
stage of an X-ray diffractometer Rigaku Rint 2400 system (Rigaku
Co., Tokyo, Japan) with Cu-Ka radiation. The X-ray diffraction
(XRD) spectra of the samples were then measured at the X-ray tube
voltage of 40 kV and the current of 200 mA.
2.5. Heat treatment of sucrose crystals
A 500 mg sample of sucrose crystals was placed in a glass vial
that had been heated at a prescribed temperature (150–220 C)
and stored in an oven (NDO-600N, EYELA Co., Tokyo, Japan) at
the prescribed temperature. Sucrose crystals that were heated at
205 C for 1 min (as well as those heated at a rate of 10 C/min
to 200 C) were dissolved in distilled water to give a final concentration
of 100 mg/mL. The resulting solution was freeze-dried and
thoroughly dehydrated, followed by an analysis of the crystallization
characteristics following the same procedures as described
above or evaluated for their protein stabilizing effect, as described
later.